Kentucky NREPC-OIS-GIS 09-2000 Frankfort Kentucky NREPC-OIS-GIS Kentucky 30 ft DEM digital raster data in ESRI GRID format A digital elevation model (DEM) contains a series of elevations ordered from south to north with the order of the columns from west to east. The DEM is formatted as one ASCII header record (A-record), followed by a series of profile records (B- records) each of which include a short B-record header followed by a series of ASCII integer elevations per each profile. The last physical record of the DEM is an accuracy record (C-record). The 7.5-minute DEM provides coverage in 7.5- by 7.5-minute blocks. Each product provides the same coverage as a standard USGS 7.5-minute quadrangle. Coverage is available for the contiguous United States, Hawaii, and Puerto Rico but is not complete. DEMs can be used as source data for digital orthophotos, and as layers in geographic information systems, for earth science analysis. DEMs can also serve as tools for volumetric analysis, for site location of towers, or for drainage basin delineation. These data were collected as part of the National Mapping Program. This DEM dataset has been reprojected to the Kentucky NAD83 Single Zone Coordinate System by Kentucky NREPC-OIS-GIS using the interpolation method specified by NADCON (NGS). 7.5-minute DEMs have rows and columns that vary in length and are staggered. The bounding coordinates form a quadrilateral (no two sides are parallel to each other), rather than a rectangle. The user will need to pad out the uneven rows and columns with blanks or flagged data values if an application requires a rectangle. Some software vendors have incorporated this function into their software for input of standard formatted USGS DEMs. en Varies ground condition Complete Irregular -89.625 -81.875 39.250 36.375 none DEM digital elevation model digital terrain model hypsography altitude height ESRIGRID U.S. Department of Commerce, 1987, Codes for the identification of the States, the District of Columbia and the outlying areas of the United States, and associated areas (Federal Information Processing Standard 5-2): Washington, D.C., National Institute of Standards and Technology. US KY None None. Microsoft Windows 2000 Version 5.0 (Build 2195) Service Pack 2; ESRI ArcCatalog 8.1.2.671ESRI GRIDKentucky NREPC-OIS-GISphysical address

500 Mero Street

FrankfortKY40601USA

14th Fl CPT

502-564-5174The original DEM dataset was provided by the U.S. Geological Survey in the NAD83 Kentucky North and South state plane coordinate zones. Applies to the original DEM: The attributes of a DEM are essentially the elevation values tied to the horizontal post positions. The accuracy of these attributes is recorded as a vertical root-mean-square error (RMSE) value in Record C of the DEM. The fidelity of the relationships encoded in the original data structure of the DEM is automatically verified using a USGS software program upon completion of the data production cycle. The test verifies full compliance to the DEM format specification. The original DEM was visually inspected for completeness on a DEM view and edit system for the purpose of performing a final quality control and, if necessary, edit of the DEM. The physical format of each digital elevation model is validated for content completeness and logical consistency during production quality control and prior to archiving in the National Digital Cartographic Data Base. Because the quadrilateral has a variable orientation in relation to the rectangular elevation grid, profiles that pass within the bounds of the DEM quadrilateral may be void of elevation grid points and, therefore may not be represented in the DEM. This condition occurs infrequently and is always the first or last profile of the data set. Level 2 DEM: Level 2 DEMs may contain void areas due to interruptions to contours in the source graphic or DLG. Void area elevation grid posts may be assigned the value of -32,767. In addition, suspect elevation areas may exist in the DEM but are not specifically identified. Suspect areas can be located on the source graphic as a disturbed surface, symbolized by contours overprinted with photo-revised or other surface pattern. Horizontal accuracy of the DEM is rarely tested or reported. For some Level-1 DEMs the horizontal accuracy of the DEM is expressed as an estimated root mean square error (RMSE). The estimate of the RMSE is based upon horizontal accuracy tests of the DEM source materials, which are selected as equal to or less than the intended horizontal RMSE error of the DEM. For DEMs without a recorded x/y RMSE, absolute horizontal accuracy can be considered the same as that for the source data and typically meets NMAS thresholds for 1:24,000-scale products (90% of points within 40 feet of true position.) No additional horizontal inaccuracy is introduced during the DEM interpolation process because the horizontal coordinates for the DEM elevation posts are derived at precisely calculated intervals. Only the vertical dimension may accrue error during the interpolation process. 0.0 Applies to the original DEM: The accuracy of a DEM is stated in the vertical dimension only. Test points used to measure DEM accuracy are well distributed, representative of the terrain, and have true elevations with accuracies well within the DEM accuracy criteria. Acceptable test points include, in order of preference, field control, aerotriangulated test points, spot elevations, or points on contours from existing source maps with appropriate contour intervals. A minimum of 28 test points per DEM is required to compute the RMSE, which is composed of a single test using 20 interior points and 8 edge points. Edge points are those located along, at, or near the quadrangle neatlines and are deemed by the editor to be useful for evaluating the accuracy of the edge of the DEM. The quality control units within the USGS collect test point data and compare the DEM with the quadrangle hypsography. There are three types of DEM vertical errors: blunder, systematic, and random. These errors are reduced in magnitude by editing but cannot be completely eliminated. Blunder errors are errors of major proportions and are easily identified and removed during interactive editing. Systematic errors follow some fixed pattern and are introduced by data collection procedures and systems. These errors may include vertical elevation shifts, misinterpretation of terrain surface because of trees, buildings and shadows, and fictitious ridges, tops, benches, or striations. Random errors result from unknown or accidental causes. DEMs are edited to correctly depict elevation surfaces that correspond to water bodies of specified size. Level 1 DEM: An RMSE of 7 meters or less is the desired accuracy standard. An RMSE of 15 meters is the maximum permitted. A 7.5-minute DEM at this level has an absolute elevation error tolerance of 50 meters (approximately three times the 15-meter RMSE) for blunder errors for any grid node when compared to the true elevation. Any array of points in the DEM cannot encompass more than 49 contiguous elevations in error by more than 21 meters (three times the 7-meter RMSE). Systematic errors that are within stated accuracy standards are tolerated. Level 2 DEM: A vertical RMSE of one-half of the contour interval, determined by the source map, is the maximum permitted. Systematic errors may not exceed one contour interval specified by the source graphic. Level 2 DEMs have been processed or smoothed for consistency and edited to remove identifiable systematic errors. Varies The accuracy of Level 1 DEMs is dependent on the flying height of the photography from which the elevations were compiled and the compilation method/equipment. Accuracy for Level 1 DEMs is often measured against an independent source of elevation data and referenced to true ground (DEM Record C, element 2.) For most Level-2 DEMs, accuracy is measured and recorded as the error introduced during the process of interpolating grid post elevations from the surrounding source contours (DEM Record C, element 5.) The accuracy (to ground) of Level 2 DEMs is actually a function of the amount of error in the source contours and in the contour interpolation process. To determine the threshold of absolute error for any particular Level-2 DEM when only the error relative to source is listed in Record C, contour-source error must also be estimated. If the source contours meet NMAS, the maximum contour-source RMSE can be determined by dividing the contour interval by 3.29. Because the source error and interpolation error cannot be assumed to be independent, the final "ground" RMSE threshold is derived by adding the source-contour RMSE to the DEM-interpolation RMSE. U.S. Geological Survey 200008 Reston, VA U.S. Geological Survey disc varies ground condition HydroDLG Hydrographic data such as streams and shorelines were converted to 3D profiles and used, during the contour interpolation process, to enforce correct position and depiction of hydrographic features on the DEM surface. The hydrographic features were collected from USGS 7.5-minute maps and revised to digital orthophoto source current as of the date specified in metadata field Calendar Date. Because contours were not revised along with the hydrography, some discrepancy between the surface water feature and surrounding terrain may be evident in areas where significant terrain change has occurred Kentucky NREPC-OIS-GIS Unknown Frankfort, KY Kentucky NREPC-OIS-GIS disc varies ground condition CONTOUR Contours digitized from the USGS 1:24,000 grpahic map. The production procedures, instrumentation, and hardware and software used in the collection of standard U.S. Geological Survey (USGS) digital elevation models (DEMs) vary depending on systems used at the contractor, cooperator, or National Mapping Division (NMD) production sites. This process step describes, in general, the process used in the production of standard USGS DEM data sets. Level 1 DEM: Level 1 DEMs are acquired photogrammetrically by manual profiling or image correlation techniques from National Aerial Photography Program (NAPP) or equivalent source photographs. Level 2 DEM: Level 2 DEMs are produced by converting 1:24,000-scale hypsography digital line graph (DLG) data to DEM format, or the DEMs are generated from vector data derived from scanned raster files of USGS 1:24.000-scale map series contour separates. Water body editing: DEM surface areas corresponding to water bodies are flattened and assigned map-specified or estimated surface elevations. Water body areas are defined as ponds, lakes, and reservoirs that exceed 0.5 inch at map scale and double line drainage that exceeds 0.25 inch at map scale. Water body shorelines are derived either from a hypsographic DLG or by interactive delineation from 1:24,000-scale USGS map series. Edge matching and edge joining: DEM data sets within a project area (consisting of a number of adjacent files) are edge-match and edge-join edited to ensure terrain surface continuity between files. Edge matching is the process of averaging adjacent elevation values along common edges within a zone of approximately 5 row or column grid posts on both edges. When edge values exceed three elevation units difference, edge joining is performed. Edge joining involves an extensive level of editing and requires editing elevation values that are internal to the DEM. This is done to create more accurate terrain representations by correcting the alignment of ridges and drains and to achieve overall topographic shaping within an approximately 25-30 row or column grid post zone on both edges. Quality control: DEMs are viewed on interactive editing systems to identify and correct blunder and systematic errors. DEMs are verified for physical format and logical consistency at the production centers using the Digital Elevation Model Verification System (DVS) software before they are archived in the National Digital Cartographic Data Base (NDCDB). DLGHYRDO; CONTOUR 200206 Raster grid cell 1 Varies State Plane Coordinate System 1600 37.083333 38.666667 -85.75 36.333333 1500000 1000000 row and column 30.0 30.0 US survey feet NAD 83 GRS_1980 6378137 298.25722210088 Kentucky NAD83 Single Zone Coordinate System - FIPS 1600 North American Vertical Datum 1988 (NAVD 88) 0.1 feet Implicit coordinate The digital elevation model is composed of an array of elevation values, each implicitly linked to derivable grid post (discrete point) location. The DEM is a gridded representation of a topographic map hypsography overlay. Each grid post entity contains a 6-character integer value between -32,767 and 32,768. U.S. Department of the Interior, U.S. Geological Survey, 1992, Standards for Digital Elevation Models: Reston, Va. Kentucky NREPC-OIS-GIS mailing address

500 Mero St

Frankfort Kentucky 40601

14th Fl CPT

USA 1-502-564-5174 1-888-275-8747 0800-1630 Monday - Friday 7.5-minute digital elevation model Although this data has been processed successfully on a computer system at the Kentucky NREPC-OIS-GIS, no warranty expressed or implied is made by the Kentucky NREPC-OIS-GIS regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty. DEM USGS standard DEM: The standard USGS DEM can be described as an ASCII formatted file of elevations preceded by a metadata header file which consists of one 1024 byte ACSII record and followed by one ASCII data quality record. Varies in NOT AVAILABLE 200206 Kentucky NREPC-OIS-GIS mailing address

500 Mero Street

14th Fl CPT

Frankfort KY 40601 USA 502 564 5174 Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998 None Unclassified None enlocal timehttp://www.esri.com/metadata/esriprof80.htmlESRI Metadata Profile 2002091815153200200209301609370020020930